Hi EWS,
Thanks for trying out Post Notif (and for the compliments)! There is not currently a shortcode, but that is an interesting idea; I will definitely add it to the list of enhancements to consider.
As for why confirmation emails are being routed to spam, that is unfortunately beyond my control. The internet’s email overlords make decisions on whether they consider an email good or spam based on the sender’s email address (so whatever email address you have defined as your sending address is being looked down upon by that particular recipient’s provider). If possible, you might want to try configuring the plugin to send from an address on a different domain.
Thanks,
Devon